The Research On Determination Of Regional Digital Height Datum Models And Their Application

The digital height datum model is not only the reference frame for the modern measuring and locating technology, but also the important basic data for the research related to the earth science, so the determination of regional digital height datum model with high resolution and high accuracy is very importance of scientific significance and practical significance.This paper mainly studied the theory, methodology and application on the determination of high-resolution and high-accuracy regional digital height datum models based on geopotential model method, "Remove-Restore" method, GNSS/Leveling method and combination method with the free data sources. The free data sources are mainly including: EGM2008 and EIGEN-6C3stat as the ultra-high-degree earth geopotential model, SRTMV4.1, SRTM30_PLUS, DTM2006.0 and RET2012 as the high-resolution digital terrain model, DTU13 as the grid gravity anomaly data, as well as the regional GNSS/Leveling data. The main results are as follows:(1) This paper determined the gravimetric quasigeoid/geoid with resolution 1’×1’in southern China(20°N-30°N,109°E-120°E) and in eastern China (28°N-38°N,113°E-123°E) by 3 determination schemes. The scheme 1 just used earth geopotential models, the scheme 2 used earth geopotential models and digital terrain models which is used for the topographic collection, and the scheme 3 used earth geopotential models, digital terrain models and the grid gravity anomaly data. After checking, the standard deviation of gravimetric quasigeoid/geoid in southern China as follow:8.4cm in Guangdong,9.7cm in A District, 4.6cm in Xuefeng Mountain and 2.9cm in Meizhou Island, and the standard deviation of gravimetric quasigeoid/geoid in eastern China as follow:3.3cm in B City and 2.6cm in Hangzhou Bay.(2) Based on the gravimetric quasigeoid/geoid in southern China and eastern China, this paper continued to lake a refinement for the regional GNSS quasigeoids which are determined by 6 fitting models in A District and B City where are sufficiently covered with the GNSS/Leveling points. As the result, the GNSS quasigeoid in A District covered 40 thousand km2 achieved 5.5cm as its best outer RMS, and the GNSS qusigeoid in B City covered 1 thousand km2 achieved 2.2cm as its best outer RMS.(3) This paper took a research on the application of the quasigeoid of southern China in long tunnels test area for height transmission. The results show that:the optimal standard deviation of height between fitting models and leveling can reach 0.7cm and the optimal standard deviation of height difference between fitting models and leveling can reach 0.8cm 100% height difference observations can satisfied the forth-order and third-order leveling, 65% height difference observations can satisfied the second-order leveling. Therefore, the result could be provided as an example for those using GNSS/Leveling to achieve the high-accuracy height transmission within long distance.(4) Combined with some existing programs, this paper developed the G Software for the regional geoid determination. G Software includes many methods, such as:geopotential model method, "Remove-Restore" method, GNSS/Leveling method and combination method, and it can take comprehensive utilization of earth geopotential models, digital terrain models, grid gravity anomaly data and GNSS/Leveling data. G Software uses extend range algorithm for the computation of associated Legendre functions under 10800 degree for every latitude without numerical overflow problem.The research results do not include any national land gravity data, so they could be the examples of regional quasigeoid/geoid determination for the area without land gravity data. With the development of space detection technology, the information of earth geopotential models are more and more completed, which could be more useful for the promotion of the methods proposed from this paper.